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Washington State University
WSU Puyallup Ornamental Plant Pathology

Bulbs and Cut Flower Research Program


Welcome to the WSU Puyallup ornamental bulb plant pathology research website. Here you will find information on about our Disease Management Program for ornamental flower bulb crops.

We are currently working with growers of many different varieties, including: daffodil, dahlia, iris, lily, peony, and tulip. Please contact-us for more information or if you’re interested in participating in our Disease Management Program.

Bulbs and cut flowers, tulip festival

Disease Management Program

Research and education on diseases of ornamental flower bulbs has been conducted at WSU Puyallup for over 80 years. As the flower bulb industry has changed with the increasing urbanization of bulb-growing regions and concern over the potential environmental impacts from pesticides, we continue to direct our research toward solutions that enable growers to minimize crop losses from plant diseases and reduce the need for pesticides.

Currently, this internationally-recognized research program focuses on the development of DNA-based assays to quantify inoculum levels of soil-borne pathogens and determine appropriate control methods. We are also evaluating reduced-risk fungicides and alternative approaches to control pre- and post- harvest diseases that affect the economic viability of the flower bulb industry.

Research Outcomes

Bulbs and cut flowers, tulip festival

  • Identification of an effective reduced-risk fungicide to control gray bulb rot.  Use of this material reduces the amount of fungicide currently used by up to 98 percent.
  • Determination that chlorine dioxide (a common, food-grade disinfectant) is as effective as formaldehyde (a more hazardous chemical) in preventing the spread of basal rot during hot water treatment of bulbs.  Gaseous forms of this material also have the potential to replace fungicide bulb dips for control of Penicillium blue mold.
  • Identification of a number of reduced-risk fungicides that provide excellent control of foliar diseases on tulips, iris, and lilies.  In some cases, the use of these materials results in a 60 percent reduction in the amount of fungicides used by growers.
  • Demonstration that peak transmission of tulip break virus by aphids occurs during late April and early May.
  • Determination that the prevalence of viruses on lilies in Washington is moderate (36.3%) and the prevalence of viruses on dahlias in Washington is high (80.9%).


Growers from Washington, Oregon, California, and British Columbia are provided the latest research information at annual Field Days and a Pacific Northwest (PNW) Flower Bulb Conference organized by WSU.

Gary leading educational activity

Partners and Support

  • Northwest Agricultural Research Foundation (NARF)
  • Wally Staatz Endowment
  • USDA Floral and Nursery Crop Research Initiative
  • WSDA Specialty Crop Block Grant
  • IR-4 program
  • Fred C. Gloeckner and Company, Inc.
  • Regional bulb and flower growers
  • Suppliers of professional products

Industry Background

Commercial flower bulb production in the PNW began over 100 years ago, and in the 1920’s, growers also supplied bulbs to greenhouse forcers in other regions of the U.S., Canada and Europe. Today, the production of both ornamental bulbs and cut flowers represents an important high-value specialty crop in the United States with 90% of the domestic production of tulips, daffodils, bulbous iris and Asiatic/oriental lilies occurring in the coastal areas of Washington, Oregon and northwestern California. In 2005, the wholesale value of flower bulb crops in the U.S. totaled over $235 million.

Currently, the majority of Washington’s specialty cut flower production occurs primarily on small farms in four counties: Clark, Lewis, Pierce, and Skagit. A WSU 2012 survey of Washington cut flower growers indicated that 98% of the growers farmed less than 10 acres and 51% of the growers farmed less than an acre.

Another WSU survey estimated there were 160 farmers markets in Washington in 2009 and 93% of these markets offered cut flowers for sale. Flowers from ornamental bulb crops are currently an important staple item at these local markets.

Cut flowers, photo credit: Edee Kulper